This invention relates generally to the fabrication of seating cushions and is particularly directed to an apparatus and method for fabricating custom contoured back and seat cushions.
Contoured support surfaces for the seat and back portions of the supported person are highly desirable for various reasons. For example, by contouring the seating surface to the configuration and dimensions of the user, the user's weight is more uniformly spread over his entire seating surface for increased comfort. Where the user is seated for long periods, such as in the case of the wheelchair-bound, the added comfort of a contoured seating surface will be evidenced in the substantially reduced tendency for the formation of pressure sores. A contoured seating surface also provides lateral support for the user which may be particularly important for the infirm or handicapped. Where one suffers from a spinal deformity and is confined for long periods to a sitting position, the additional support and comfort may be absolutely essential for the well-being of that person. The support structures used in such contoured seats should therefore be relatively soft in consistency, yet firm enough to provide the desired support for even the most infirm.
The prior art discloses various approaches in the fabrication and construction of contoured seating surfaces. One such approach makes use of a contoured urethane foam base upon which is positioned a pad containing a fluid which generally assumes the contour of the seating surface of the user. The fluid flows through various channels internal to the pad so as to prevent the "bottoming out" of the pad. In order to accommodate the flow of fluid within the pad and to assume a range of seating surface configurations and dimensions, the pad is provided with an oversized elastic casing which results in an uneven, irregular seating surface upon which the user is positioned.
Another approach in the formation and fabrication of contoured seating cushions involves the use of an airtight flexible bag filled with a granular material which assumes the general contour of a person positioned thereon. With the person to be fitted positioned thereon, the airtight bag is evacuated in order to maintain the granular material in conformance with the seating contour of the person fitted. To maintain the desired shape, a high vacuum must be maintained within the flexible bag which is difficult, if not impossible, to maintain for sustained periods without employing expensive materials and sophisticated fabrication techniques. In addition, while under vacuum the granular material is maintained rigidly in place and presents a hard support surface for the user. In addressing the problem of maintaining a high vacuum within the bag for prolonged periods, the granular material may be coated with an adhesive which can be activated by exposing the bag to microwave radiation in order to convert the mass of granular material to a permanently rigid body. One example of this approach is taught in U.S. Pat. No. 4,493,877 to Burnett.
Other approaches to the formation of contoured seat cushions have involved the carving out and shaping of a cushion material in accordance with the user's shape and size. This approach is tedious and of limited accuracy in fitting the cushion to the user's dimensions. Other approaches have made use of vacuum tables upon which a plaster positive of the contour of the person to be fitted is positioned with a cushion cover such as vinyl positioned over the plaster positive and the vacuum table. A foam is then poured over the cover and is allowed to cure in forming the contoured cushion. The vacuum is released, and the cushion is then removed from the vacuum table. Apparatus used in this cushion forming technique suffer from various limitations. For example, no provision is made for fabricating cushions over a wide range of width, length and depth dimensions in order to satisfy individual user requirements, particularly when applied to those suffering from extreme physical deformity. In addition, the range of contour variation is limited primarily because of the manner in which the vinyl is drawn under vacuum and limitations in the flexibility of the vinyl itself. These vacuum table arrangements have also been generally unreliable and have failed to maintain a high vacuum during the fabrication procedure resulting in inaccurately formed cushions.
The present invention overcomes all of the aforementioned limitations of the prior art by providing an apparatus and method for fabricating contoured seating cushions having a wide range of dimensions and virtually any surface configuration which may be precisely matched to the seating contour of the intended user. The apparatus and method of the present invention not only facilitates the fabrication of contoured seating cushions, but also substantially increases the reliability of the process in providing more accurately contoured cushions.